Department of Geosciences
North Dakota State UniversityWEB-PHREEQC:
AQUEOUS GEOCHEMICAL MODELLING

What is aqueous geochemical modelling?

For the purposes of this course, we can begin with considering aqueous geochemical modelling to be the calculation of:

equilibrium concentrations (or activities) of chemical species in solution, and

the saturation indices (SI's) of solid phases in equilibrium with a solution.

from a chemical analysis (real or hypothetical) of a solution.

A slightly broader definition includes the calculation of the effects of mixing of waters, adding phases to the solution, changing the solution's temperature, Eh, or pH, etc.

Approximations of this kind of calculation can be done on a hand calculator or on a spreadsheet. More detailed calculations can be done using computer programs such as PHREEQC, WATEQ4F, MINTEQ, EQ3/6, ChemEQL, GEMS, and the Geochemist's Workbench.